In source build failure not explained

[hippo91]

When trying to build Kokkos in its source tree, the procedure fails which is a good thing.
However there is no explanation about it:

cmake .
-- Setting default Kokkos CXX standard to 11
CMake Error at /usr/share/cmake-3.13/Modules/CMakeDetermineSystem.cmake:174 (file):
  file attempted to write a file:
  /home/anaxi/PROGRAMMATION/CPP/kokkos/CMakeFiles/CMakeOutput.log into a
  source directory.
Call Stack (most recent call first):
  CMakeLists.txt:89 (PROJECT)


CMake Error: CMake was unable to find a build program corresponding to "Unix Makefiles".  CMAKE_MAKE_PROGRAM is not set.  You probably need to select a different build tool.
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!

Maybe it could be clearer to have an output which looks like:

cmake .
CMake Error at CMakeLists.txt:4 (message):
  FATAL: In-source builds are not allowed.

                         You should create a separate directory for build files.


-- Configuring incomplete, errors occurred!

[dalg24]

We disallow in-source builds here

kokkos/CMakeLists.txt

Line 69 in 605ab03

set(CMAKE_DISABLE_IN_SOURCE_BUILD ON)

Admittedly, this yield a rather cryptic error message.